Electrical resistance seam welding method and apparatus

Abstract

An electric resistance seam welding method and apparatus includes a continuous wire electrode which is passed successively over a first electrode reel and thereafter over a second electrode reel via a plurality of guide and deflection rollers, the outer surfaces of the wire confronting each other when passing over the reels and being pressed together by the reels by a predetermined welding force against interposed workpieces to be seam welded together. An electric current is applied so as to pass from the second electrode reel to the first reel through the wire electrode and the interposed workpieces, and the wire electrode is motor driven for feeding the workpieces through the reels. A copper wire is utilized as the wire electrode and has a tensile strength at the elastic limit of between 11 and 13 kg-f/mm 2 and has a percentage elongation at break of 26 to 17%. The reels are pressed together by a force of 60 to 70 kg, and the copper wire is subject to a tensile stress of less than 10 kg-f/mm 2 while passing over and between the reels. The reels are maintained at an operating temperature of 10° to 30° C. as the wire electrode passes thereover, so that a maximum elongation of the wire of 6% when passing over the first reel, and a maximum further elongation of the wire of 6% when passing over the second reel, is attained.

What is claimed is: 
     
       1. An electrical resistance seam welding method in which a continuous wire electrode is passed successively over a first electrode reel and over a second electrode reel, via a plurality of guide and deflection rollers, said wire electrode passing over said reels in confronting relationship and being pressed together by said reels, by a predeterminded welding force, against interposed workpieces to be seam welded together, an electric current being applied which passes from one of said reels to the other of said reels through said wire electrode and said interposed workpieces, said wire electrode being motor driven for feeding the workpieces through said reels, the improvement comprising utilizing a copper wire as said wire electrode having a tensile strength at the elastic limit of between 11 and 13 kg-f/mm 2  and having a percentage elongation at break in the range of 26 and 17% pressing said reels together by a force of 60 to 70 kg, said copper wire being subject to a tensile stress of less than 10 kg-f/mm 2  while passing over and between said reels, and maintaining said reels at an operating temperature of 10° to 30° C., so that a maximum elongation of said wire of 6% when passing over said first reel, and a maximum further elongation of said wire of 6% when passing over said second reel, is obtained. 
     
     
       2. The method according to claim 1, further comprising utilizing said copper wire having the tensile strength at the elastic limit of approximately 12 kg-f/mm 2 , and the percentage elongation at break of approximately 21%. 
     
     
       3. The method according to claim 1, further comprising imparting to said copper wire a tensile stress of 2 to 6 kg-f/mm 2  while passing over and between said reels. 
     
     
       4. The method according to claim 1, further comprising a motor driving said second reel for driving said copper wire about said reels which effects a rotation of said first reel and a forward advancing of said interposed workpieces, and imparting to said copper wire a maximum tensile stress of 6 kg-f/mm 2  before said wire reaches said first reel. 
     
     
       5. The method according to claim 1, further comprising pulling said copper wire away from said second reel for imparting thereto a tensile stress of 10 kg-f/mm 2  maximum. 
     
     
       6. The method according to claim 1, further comprising selecting said copper wire as initially having a round cross-section and a tensile strength at the elastic limit of less than 11 kg-f/mm 2  and a percentage elongation at break of more than 30%, and thereafter reshaping said copper wire into a substantially rectangular cross-sectional shape, the reshaping being carried out by passing the wire of round cross-section through the nip of a pair of press rollers to thereby reduce the cross-sectional area of the wire by 10% maximum. 
     
     
       7. The method according to claim 4, further comprising applying to said copper wire a weight- or spring-loaded dancing roller between said pair of press rollers and said first reel for maintaining a tensile stress in said wire at a substantially constant value in the range of 3 to 6 kg-f/mm 2  between said press rollers and said first reel. 
     
     
       8. An electric resistance seam welding apparatus including a frame having edge confronting first and second electrode reels and as well as guide and deflection rollers rotatably mounted thereon, a continuous wire electrode arranged for successively passing over said first reel and then over said second reel via said guide and deflection rollers, means for driving one of said reels, means for pressing said reels together by a welding force of 60 to 70 kg for applying said force against overlapping workpiece ends disposed between portions of said wire which pass over said reels, means for applying an electric current which passes from one of said reels to the other of said reels through said wire electrode and the interposed workpiece ends for seaming them together, means for cooling said reels to an operating temperature in the range of 10° to 30° C., said wire electrode comprising a copper wire having a tensile strength at the elastic limit of 11 to 13 kg-f/mm 2  and a percentage elongation at break in the range of 26 to 17%, before passing over said first reel, said driving means rotating said second reel which, by means of said copper wire, rotates said first reel, whereby said copper wire between said reels is subject to a tensile stress of less than 10 kg-f/mm 2 . 
     
     
       9. The apparatus according to claim 8, wherein the tensile strength of said wire at the elastic limit is about 12 kg-f/mm 2  and the percentage elongation at break of said wire is about 20%. 
     
     
       10. The apparatus according to claim 8, wherein said tensile stress of said wire is 6 kg-f/mm 2  maximum between said reels. 
     
     
       11. The apparatus according to claim 8, further comprising means for pulling said copper wire away from said second reel so as to effect a wire tensile stress of 10 kg-f/mm 2  maximum. 
     
     
       12. The apparatus according to claim 8, wherein said copper wire initially has a round cross-section, a tensile strength at the elastic limit of less than 11 kg-f/mm 2  and a percentage elongation at break of more than 30%, a motordriven pair of press rollers being provided for pressing the copper wire into a shape substantially rectangular in cross-section while reducing the cross-sectional area of said wire by 10% maximum. 
     
     
       13. The apparatus according to claim 12, further comprising a weight- or spring-loaded dancing roller located between said press rollers and said first reel for effecting a wire tensile stress of 3 to 6 kg-f/mm 2  before passing over said first reel.